In humans, chemical digestion is accomplished

A. by enzyme action that begins in the mouth and ends in the

B. esophagus

C. stomach

D. small intestine

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Answer Explanation:

C) small intestine

- Correct: Chemical digestion in humans is a complex process involving various enzymes acting on different nutrients. While digestion does begin in the mouth with the action of enzymes like salivary amylase on carbohydrates, the majority of chemical digestion occurs in the small intestine. Enzymes secreted by the pancreas (such as pancreatic amylase, lipase, and proteases) and the small intestine itself (such as maltase, sucrase, lactase, and peptidases) break down carbohydrates, fats, and proteins into smaller molecules. Additionally, bile salts produced by the liver and stored in the gallbladder aid in the emulsification and digestion of fats in the small intestine. Therefore, chemical digestion largely concludes in the small intestine before nutrients are absorbed into the bloodstream.

A) esophagus

- Incorrect: The esophagus is primarily involved in the mechanical process of swallowing, which pushes food down into the stomach. While some minor enzymatic activity may occur due to saliva coating the food during swallowing, significant chemical digestion does not occur in the esophagus.

B) stomach

- Incorrect: While the stomach does play a role in chemical digestion, particularly in the breakdown of proteins by the enzyme pepsin and the denaturation of proteins by hydrochloric acid, the majority of chemical digestion occurs in the small intestine. The stomach mainly serves to mechanically churn food and begin the process of protein digestion.

D) gallbladder

- Incorrect: The gallbladder stores and releases bile produced by the liver, which aids in the emulsification and digestion of fats in the small intestine. However, the gallbladder itself is not directly involved in chemical digestion, and the majority of digestive enzymes are not secreted or stored in the gallbladder.

Therefore, the Correct Answer is C.

More Questions on Digestive System Practice Exam 1

Question 1:

Which process is represented by the diagram below?

A. emulsification

B. excretion

C. absorption

D. peristalsis

The Correct Answer is A.

Emulsification is a process by which large fat globules are broken down into smaller droplets. This process is facilitated by substances called emulsifiers, with bile being one of the most common emulsifiers in the human body.


Question 2:

Salmonella bacteria can cause humans to have stomach cramps, vomiting, diarrhea, and fever. The effect these bacteria have on humans indicates that Salmonella bacteria are

A. predators

B. pathogenic organisms

C. parasitic fungi

D. decomposers

The Correct Answer is B.

B) pathogenic organisms

- Correct: Salmonella bacteria are pathogenic organisms, meaning they can cause disease in humans and other animals. When ingested, Salmonella bacteria can lead to symptoms such as stomach cramps, vomiting, diarrhea, and fever. Salmonella infection, known as salmonellosis, is a common cause of foodborne illness, often associated with the consumption of contaminated food, particularly undercooked poultry, eggs, and unpasteurized dairy products.

A) predators

- Incorrect: Predators are organisms that hunt, kill, and consume other organisms for food. Salmonella bacteria are not predators; they do not actively hunt and consume other organisms.

C) parasitic fungi

- Incorrect: Salmonella bacteria are not parasitic fungi. Parasitic fungi are fungi that derive nutrients from living organisms, often causing harm or disease. Salmonella bacteria are a distinct type of pathogenic bacteria, not fungi.

D) decomposers

- Incorrect: Decomposers are organisms that break down and feed on dead organic matter, aiding in the process of decomposition. Salmonella bacteria are not decomposers; they are pathogenic bacteria that can cause illness in humans and animals.


Question 3:

All of the following are organs of the digestive system except

A. the stomach

B. the mouth

C. the intestines

D. the heart

The Correct Answer is D.

A) The stomach - This is an organ of the digestive system. It plays a crucial role in breaking down food through the secretion of gastric juices, which contain enzymes and acids to begin the process of digestion. Therefore, option A is correct.

B) The mouth - The mouth is also an organ of the digestive system. It is where the process of digestion begins, as it is responsible for chewing and breaking down food into smaller pieces. Additionally, saliva produced in the mouth contains enzymes that start the chemical breakdown of food. Therefore, option B is correct.

C) The intestines - Both the small intestine and the large intestine are essential organs of the digestive system. The small intestine is where most of the absorption of nutrients from food occurs, while the large intestine absorbs water and salts from the material that has not been digested. Therefore, option C is correct.

D) The heart - The heart is not an organ of the digestive system. Instead, it is a part of the circulatory system responsible for pumping blood throughout the body. While the circulatory system works in conjunction with the digestive system to transport nutrients absorbed from the intestines to various tissues and organs, the heart itself is not directly involved in digestion. Therefore, option D is incorrect.


Question 4:

In humans, structures that release digestive secretions directly into the small intestine include both the

A. salivary glands and the pancreas

B. gall bladder and the lacteals

C. villi and the salivary glands

D. pancreas and the gall bladder

The Correct Answer is D.

D) pancreas and the gallbladder

- Correct: Both the pancreas and the gallbladder release digestive secretions directly into the small intestine. The pancreas secretes pancreatic enzymes (such as amylase, lipase, and proteases) into the small intestine to aid in the digestion of carbohydrates, fats, and proteins. The gallbladder stores bile produced by the liver, which is released into the small intestine to aid in the emulsification and digestion of fats.

A) salivary glands and the pancreas

- Incorrect: While the pancreas releases digestive secretions directly into the small intestine, the salivary glands secrete saliva into the mouth, which contains enzymes (such as amylase) that begin the digestion of carbohydrates. Salivary glands do not release digestive secretions directly into the small intestine.

B) gall bladder and the lacteals

- Incorrect: The gallbladder stores bile produced by the liver, which is released into the small intestine to aid in fat digestion. Lacteals are lymphatic vessels found in the villi of the small intestine and are involved in the absorption of fats, but they do not release digestive secretions directly into the small intestine.

C) villi and the salivary glands

- Incorrect: Villi are finger-like projections in the small intestine that increase the surface area for absorption of nutrients but do not release digestive secretions directly into the small intestine. Salivary glands secrete saliva into the mouth to initiate the digestion of carbohydrates but do not release digestive secretions directly into the small intestine.


Question 5:

A branch of the nerve regulating the secretions of the stomach can be cut surgically. The decrease in hydrochloric acid secretion that would result from this procedure would be most helpful to an individual with

A. diarrhea

B. appendicitis

C. gallstones

D. ulcers

The Correct Answer is D.

D) ulcers

- Correct: The decrease in hydrochloric acid secretion resulting from the surgical cutting of a branch of the nerve regulating stomach secretions would be most helpful to an individual with ulcers. Ulcers are sores or lesions that develop in the lining of the stomach, small intestine, or esophagus due to factors such as infection with Helicobacter pylori bacteria, prolonged use of nonsteroidal anti-inflammatory drugs (NSAIDs), or excessive alcohol consumption. Hydrochloric acid plays a significant role in the formation and exacerbation of ulcers by increasing the acidity of the stomach, which can irritate and erode the lining of the gastrointestinal tract. Therefore, reducing hydrochloric acid secretion can help alleviate the symptoms and promote healing of ulcers.

A) diarrhea

- Incorrect: Decreasing hydrochloric acid secretion would not directly address the underlying causes of diarrhea, which may be related to infections, dietary issues, or other factors affecting gastrointestinal motility and water absorption.

B) appendicitis

- Incorrect: Appendicitis is inflammation of the appendix, a small pouch located near the junction of the small and large intestines. Decreasing hydrochloric acid secretion would not directly affect the development or treatment of appendicitis.

C) gallstones

- Incorrect: Gallstones are hardened deposits that form in the gallbladder and can obstruct the flow of bile. Decreasing hydrochloric acid secretion would not directly address the formation or treatment of gallstones, as they are primarily composed of cholesterol or bilirubin, not affected by changes in stomach acid levels.


Question 6:

Which components of the human diet contain the greatest amounts of sugars and starches?

A. meat and eggs

B. fruits and vegetables

C. minerals and milk

D. water and vitamins

The Correct Answer is B.

B) fruits and vegetables

- Correct: Fruits and vegetables contain the greatest amounts of sugars and starches in the human diet. Both fruits and vegetables are rich sources of carbohydrates, including natural sugars, fiber, and starches. These carbohydrates provide a readily available source of energy for the body. Examples of fruits with natural sugars include apples, bananas, and grapes, while starch-containing vegetables include potatoes, corn, and peas.

A) meat and eggs

- Incorrect: Meat and eggs are primarily sources of proteins and fats, not sugars and starches. They contain minimal amounts of carbohydrates.

C) minerals and milk

- Incorrect: Minerals are inorganic compounds essential for various physiological functions, and milk is a source of proteins, fats, and carbohydrates (mainly lactose, a sugar). While milk contains some sugars, fruits and vegetables typically contribute more significant amounts of sugars and starches to the diet.

D) water and vitamins

- Incorrect: Water and vitamins are essential components of the diet, but they do not contain sugars and starches. Water is a vital component for hydration, and vitamins are organic compounds required for various biochemical processes in the body.


Question 7:

Base your answer to the following question on the diagram below.

A digestive function of organ C is the synthesis and secretion of

A. salivary amylase

B. protease

C. hydrochloric acid

D. bile

The Correct Answer is B.

Protease enzymes are responsible for breaking down proteins in our food into amino acids. Then different enzymes join amino acids together to form new proteins needed by the body for growth and repair. Protease enzymes are produced in pancreas.


Question 8:

Feces is usually about 40 percent water and 60 percent solid matter. Reducing the water content to 20 percent would most likely result in

A. ulcers

B. appendicitis

C. diarrhea

D. constipation

The Correct Answer is D.

D) constipation

- Correct: Feces with reduced water content, such as reducing the water content to 20 percent, would result in constipation. Constipation refers to infrequent bowel movements or difficulty passing stool, often characterized by hard, dry, and difficult-to-pass stools. When feces have less water content, they become harder and drier, making them more difficult to pass through the intestines. This can lead to discomfort, straining during bowel movements, and a sense of incomplete evacuation.

A) ulcers

- Incorrect: Ulcers are sores or lesions that develop in the lining of the digestive tract, commonly in the stomach or the upper part of the small intestine. They are not directly related to changes in the water content of feces.

B) appendicitis

- Incorrect: Appendicitis is inflammation of the appendix, a small pouch located near the junction of the small and large intestines. It is not directly related to changes in the water content of feces.

C) diarrhea

- Incorrect: Diarrhea refers to frequent, loose, or watery bowel movements. Reduced water content in feces would lead to constipation rather than diarrhea.


Question 9:

The pancreas is an organ connected to the digestive tract of humans by a duct (tube) through

A. which digestive enzymes flow. These enzymes are important to the digestive system because

B. they

C. form proteins needed in the stomach

D. form the acids that break down food

The Correct Answer is C.

The enzymes secreted by the pancreas play a crucial role in the digestion process by breaking down various nutrients, such as carbohydrates, proteins, and fats, into smaller molecules.

These smaller molecules are then absorbed through the walls of the small intestine into the bloodstream and subsequently transported to cells throughout the body for energy production, growth, and repair.

Therefore, these enzymes are essential for converting complex food substances into molecules that can be utilized by the body's cells for various metabolic processes.


Question 10:

Which foods should be included in a balanced diet as a good source of roughage?

A. red meat and poultry

B. fresh fruits and vegetables

C. eggs and milk products

D. animal fat and plant oil

The Correct Answer is B.

B) fresh fruits and vegetables

- Correct: Fresh fruits and vegetables are excellent sources of roughage, also known as dietary fiber. These foods provide insoluble fiber, soluble fiber, or a combination of both, which adds bulk to the stool and promotes healthy digestion. Insoluble fiber, found in foods like leafy greens, celery, and broccoli, helps to move food through the digestive tract, preventing constipation. Soluble fiber, found in foods like apples, oats, and beans, can help lower cholesterol levels and regulate blood sugar levels.

A) red meat and poultry

- Incorrect: While red meat and poultry are good sources of protein and other nutrients, they are not significant sources of dietary fiber or roughage. These foods do not contribute to the fiber content of the diet.

C) eggs and milk products

- Incorrect: Eggs and milk products are valuable sources of protein, vitamins, and minerals, but they are not significant sources of dietary fiber or roughage. These foods do not provide the fiber needed for healthy digestion.

D) animal fat and plant oil

- Incorrect: Animal fat and plant oils are sources of dietary fat, which is important for providing energy and essential fatty acids in the diet. However, they do not contain significant amounts of dietary fiber or roughage. These foods do not contribute to the fiber content of the diet.